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- Rika was the first boss ever in a Touhou shooting game.
- She's also the first Extra Stage boss.
- Rika is the only character in the series to pilot a vehicle during a boss fight - tanks that she herself constructed.
- Description: Has red caterpillar tracks with a gray turret. The turret has a Yin-Yang orb on top. Many leaves hang (push?) From the rear of the turret. Vines hang (push?) Around the main gun.
- Description: Has a red pupil and black eyelids. Has two large purple wings, a halo, and two large tentacles. Below there is something green (leaves?). On the lower eyelid is the eighteenth letter of the Greek alphabet, sigma (Σ).
- The Evil Eye Sigma is a flying tank.
- It is considered by many to be the most difficult extra boss in the series.